Analysis of the Bitcoin UTXO set

Bitcoin relies on the Unspent Transaction Outputs (UTXO) set to efficiently verify new generated transactions. Every unspent out- put, no matter its type, age, value or length is stored in every full node. In this paper we introduce a tool to study and analyze the UTXO set, along with a detailed description of the set format and functionality. Our analysis includes a general view of the set and quantifies the difference between the two existing formats up to the date. We also provide an ac- curate analysis of the volume of dust and unprofitable outputs included in the set, the distribution of the block height in which the outputs where included, and the use of non-standard outputs

Efficient State Management in Distributed Ledgers

Distributed ledgers implement a storage layer, on top of which a shared state is maintained in a decentralized manner. In UTxO-based ledgers, like Bitcoin, the shared state is the set of all unspent outputs (UTxOs), which serve as inputs to future transactions. The continuously increasing size of this shared state will gradually render its maintenance unaffordable. Our work investigates techniques that minimize the shared state of the distributed ledger, i.e., the in-memory UTxO set. To this end, we follow two directions: a) we propose novel transaction optimization techniques to be followed by wallets, so as to create transactions that reduce the shared state cost and b) propose a novel fee scheme that incentivizes the creation of state-friendly transactions. We devise an abstract ledger model, expressed via a series of algebraic operators, and define the transaction optimization problem of minimizing the shared state; we also propose a multi-layered algorithm that approximates the optimal solution to this problem. Finally, we define the necessary conditions such that a ledger’s fee scheme incentivizes proper state management and propose a state efficient fee function for Bitcoin

On Symbolic Verification of Bitcoin's script Language

Validation of Bitcoin transactions rely upon the successful execution of scripts written in a simple and effective, non-Turing-complete by design language, simply called SCRIPT. This makes the validation of closed scripts, i.e. those associated to actual transactions and bearing full information, straightforward. Here we address the problem of validating open scripts, i.e. we address the validation of redeeming scripts against the whole set of possible inputs, i.e. under which general conditions can Bitcoins be redeemed? Even if likely not one of the most complex languages and demanding verification problems, we advocate the merit of formal verification for the Bitcoin validation framework. We propose a symbolic verification theory for of open SCRIPT, a verifier tool-kit, and illustrate examples of use on Bitcoin transactions. Contributions include 1) a formalisation of (a fragment of) the language; 2) a novel symbolic approach to SCRIPT verification, suitable, e.g. for the verification of newly defined and non-standard payment schemas; and 3) building blocks for a larger verification theory for the developing area of Bitcoin smart contracts. The verification of smart contracts, i.e. agreements built as transaction-based protocols, is currently a difficult to formalise and computationally demanding problem

securePrune:Secure block pruning in UTXO based blockchains using Accumulators

In this paper, we propose a secure block pruning scheme called securePrune for reducing the storage space of a full node and synchronization time of bootstrapping nodes joining the Peer-to-Peer (P2P) network in an Unspent Transaction Outputs (UTXO) based blockchain like bitcoin using RSA accumulators. In our scheme, the miners periodically release a snapshot of the blockchain state (UTXO set), the other full nodes in the network, securely prune the historical blocks after attaining the required number of confirmations to the snapshot block. This is achieved through the modification of the block structure by including a representation for the state as an RSA accumulator called accumulator state in the block header and proofs of knowledge for deletion/inclusion of the current block's input/output transactions in the block. The secure and periodic pruning of the old blocks, reduce the synchronization time for a new node joining into the network. The simulation results demonstrate a significant reduction in the storage space of a full node and the bootstrapping cost of the new nodes. © 2021 IEEE

Decentralized Consensus Mechanisms in Blockchain: A Comparative Analysis

Blockchain technology relies on decentralized consensus mechanisms that allow distributed networks of nodes to agree on the state of a ledger without central coordination. This paper provides a comparative analysis of major consensus protocols utilized in blockchain systems, including proof-of-work (PoW), proof-of-stake (PoS), delegated proof-of-stake (DPoS), practical Byzantine fault tolerance (PBFT), and federated consensus. We analyze the core principles behind each mechanism, strengths and weaknesses in terms of security, scalability, energy efficiency, and decentralization. We also provide examples of major blockchain platforms utilizing these protocols. Our analysis finds that no consensus mechanism optimizes across all attributes, with inherent tradeoffs between decentralization, transaction throughput, energy use, and finality. Hybrid models are emerging which aim to balance these tradeoffs

A Survey on Coin Selection Algorithms in UTXO-based Blockchains

Coin selection algorithms are a fundamental component of blockchain technology. In this paper, we present a comprehensive review of the existing coin selection algorithms utilized in unspent transaction output (UTXO)-based blockchains. We provide a list of the desired objectives and categorize existing algorithms into three types: primitive, basic, and advanced algorithms. This allows for a structured understanding of their functionalities and limitations. We also evaluate the performance of existing coin selection algorithms. The aim of this paper is to provide system researchers and developers with a concrete view of the current design landscape

Study and Implementation of Blockchain Compression

Blockchain technology is being recognized as the technology innovation that is going to change how society and people interact. Despite the excitement, these application require hundred of gigabyte of memory space and they are not suitable for IoT devices. Our research goals are to compress the blockchain data and to measure the minimum memory required to participate in a blockchain application maintaining both privacy and security